Flotation of magnesite



Patented Apr. 10,

UN lT-ED FLOTATION F MAGNESITE John W. Leiforge, near Columbia, Tenn.

No Drawing-s Claims.

"magnesian ores by froth flotation methods, and

more particularly to the production of magnesite from ores containing other magnesium compounds.

It has been proposed to. separate magnesite from ore containing calcium carbonate and silica by theuse of oleic acid and small amounts of carbon dioxide as conditioner. It has also been proposed to concentrate talc from ore containing magnesite by the use of frothers and magnesite depressants. It has further been proposed to separate magnesite from serpentine and quartz by flotation after treatment of finely divided ore with cationic collectors.

The principal object of the present invention is to separate magnesite from ore containing magnesite (MgCOa) and serpentine (3MgO'2SiO2).

Such ore may also contain impurities such as talc, anthophyllite and chromite. Another object of this invention is to provide an eflicient and economical method for the separation of magnesite from serpentine adaptable for use in standard flotation apparatus. Other objects of this invention include the provision of a method for the concentration of magnesite in order to produce material suitable for the production'of refractories.

The present invention is directed to a process for the separation of magnesite from a mixture of serpentine and magnesite by agitating and aerating an aqueous pulp of said mixture with barium chloride for a time sufllcient to activate said magnesite by barium ions from said chloride, and by agitating and aerating the aqueous pulp containing serpentine and said magnesite so activated with oleic acid to produce and remove a froth containing said magnesite substantially free form serpentine.

In one of the ores in which the present invention is particularly effective, the magnesite is distributed through the serpentine in extremely irregular islands ranging in size from slightly less than one millimeter down to less than one-tenth of a millimeter. The particles less than one-tenth of a millimeter were numerous, but made up a small fraction of the total magnesite. Where magnesite made up more than one-half of the rock, the serpentine flakes were felted roughly parallel to each other and to the surface of the masnesite grains. Frequently, in zones of con- STATES PATENT OFFICE Application August 2, 1944, erial No. 547,761

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 157) centrated magnesite, the magnesite was in elongated grains in subparallel arrangement. The structure of the rock was such that fractures followed the cleavage of the serpentine rather than of the harder magnesite.

Petrographicahy, the rock consisted of finely divided magnesite in a felted matrix of serpentine minerals (serpophite and antigroite, but no 'chrysotile), with minor talc, anthophyllita and primary chromite. Magnesite and serpentine were the structurally important components, with the minor amount of talc as flakes similar to the flaky serpentine. Magnesite made up from 0 to 30 percent of difierent samples of the rock, not counting the local concentration of magnesite into veins.

One example of the operation of the present invention is given for the flotation of serpentine containing, in per cent: MgO, 37.3; F6203, 10.9; AlaQa, 1.6; SiOz, 33.8; and CO2, 10.6. The serpentine was ground to a fineness suitable for flotation 96.5% less than 150 mesh, transferred to flotation cell and diluted to a 20% suspension. The pH of the pulp was adjusted to 9.5, pine oil was added and the pulp agitated and aerated to produce and remove a froth consisting chiefly of talc, anthophyllite, primary chromite and other impurities. To the remaining aqueous pulp was added an amount of barium chloride equivalent to 0.8 pound per ton of ore and the mixture was agitated and aerated for approximately four minutes, a time sufficient to activate the magnesite therein by barium ions from the barium chloride. Thereafter, oleic acid in an amount equivalent to 0.43 pound per ton was added to the aqueous pulp containing the serpentine and magnesite so activated, and on agitating and aerating a froth containing magnesite substantially free from serpentine was produced and removed from the pulp. The froth consisted of about magnesite and the residual tailing was largely serpentine.

It was observed that too rapid introduction of air caused magnesite to float along with the talc during the initial separation after treatment of the pulp with pine oil. When the air was controlled carefully the froth showed a sharp subsidence that showed that the tale flotation was complete and that a satisfactory separation had been obtained. Although the magnesite may be separate from the serpentine in a pulp varying 2 as'rams with amounts as low as 0.2 pound per ton with a probable maximum eiliciency with amounts from 0.8 to 1.0 pound per ton. Oleic acid in amounts between 0.25 and 0.5 pound per ton is required to serve as a collector of the magnesite after activation with barium ions. Stepwise addition of the oleic acid collector decreased the amount required and brought about some improvement in the grade of the ma nesite separated.

It will be seen, therefore. that this invention actually may be carried out by the use of various modifications and changes without departing from its spirit and scope.

- I claim:

1. A process for the separation oi magnesite from a mixture of serpentine and magnesite with impurities, including talc, anthophyilite, and primary chromite, which comprises (a) agitating and aerating aqueous pulp of said mixture with pine oil to produce and remove a froth containing chiefly talc and other said impurities in said mixture. (b) agitating and aerating the remaining aqueous pulp containing serpentine and magnesite with barium chloride for a time willcient to activate said magnesite by barium ions from said chloride, and (c) agitating and aerating the aqueous pulp, containing serpentine and said magnesite so activated, with oleic acid to produce and remove a troth containing said magnesite substantially free from serpentine.

2. A process for the separation of magnesite from a mixture of serpentine and magnesite, which comprises (a) agitating and aerating an aqueous pulp of said mixture with barium chlo-- ride for a time suflicient to activate said magnesite by barium ions from said chloride, and (b) 10 agitating and aerating the aqueous pulp con- 20 said aqueous pulp is added to activate said magnesite.

5. Process according to claim 2 wherein (a) 0.25 to 0.5 pound or oieic acid per ton of mixture in said aqueous pulp is added to collect said mag- 25 nesite in said aqueous pulp.

JOHN W. LEFFORGE. 

